1. Field of Invention
This invention relates to field of delivering genetic material into cells, specifically to an improved particle bombardment apparatus for delivering genetic material into living cells.
2. Discussion of Prior Art
Particle-mediated delivery of genetic material into living cells has become a powerful tool for medical research and biotechnology. Existing particle bombardment devices propel inert or biologically active particles at speeds great enough to penetrate the surface of cells. These particles are typically used as carriers to deliver genetic material or transgenes into target cells in vivo or in vitro. The transgenes may then integrate into the germ line of plant and animal cells.
Judging from recent advances in gene therapy research, many diseases may eventually be treated by the transformation of patient cells with appropriate transgenes. However, existing particle bombardment systems are inadequate for delivering high-speed particles to fragile in vivo cells such as, but not limited to, those found in lung or embryonic tissue. Firstly, many current devices use mechanisms of particle delivery that are harmful to fragile cells. Most cells can recover from the penetration of the actual particles, but collateral damage from secondary blast effects destroys some types of cells. Secondly, there is presently no endoscopic particle bombardment device capable of delivering particles at a high speed through a flexible or convoluted passageway of varying shape or dimension. Therefore, many human cells in vivo are currently physically inaccessible for particle bombardment gene therapy.
Many apparatuses and methods have been used to accelerate particles into cells, but often, many damage target cells in the process. For example, in one method disclosed by U.S. Pat. No. 4,945,050 to Sanford (1990), particles are entrained in a pressurized stream of gas through a barrel and are thereby accelerated to the target. However, the use of gas pressures sufficient to accelerate particles enough to penetrate cells often result in damage to fragile cells via a blast effect from the gas itself. Most plant cells, and certain animal cells can withstand the blast, but many types of cells cannot. As an attempt to address this issue, U.S. Pat. No. 5,525,510 (1995) to Dennis McCabe discloses an exit nozzle with a conical taper used to disperse the blast effect. While this design does slightly reduce the effect of the blast, it still does not prevent damage to certain types of animal cells.
In another method disclosed by U.S. Pat. No. 4,945,050 to Sanford (1990), a macroprojectile or bullet is used to accelerate particles. An explosive charge accelerates the bullet along with particles in a forward chamber through a barrel. At the exit port, a stop plate with an aperture stops the bullet but allows the particles to continue toward the target. There are exhaust vents present near the muzzle to divert compressed gas ahead of the bullet so as to reduce blast effects. Nevertheless, this design also cannot be used for endoscopic applications since the cylindrical nature of the bullet does not allow the delivery of particles through a convoluted or flexible barrel or corridor of varying shape.
In another popular method disclosed by U.S. Pat. No. 5,506,125 to Dennis McCabe (1996), particles are accelerated on a carrier sheet. A retaining screen stops the carrier sheet but allows the particles to continue on their course toward the cells. The blast effect from this method is, in general, less pronounced; but since aerodynamic drag significantly slows the particles in the space between the retaining screen and the target, partial evacuation of the test chamber is necessary. However, cell viability is reduced at pressures less than 200 millibars. Additionally, evacuation is not even feasible if the target cells are internal in vivo cells from a human patient. Furthermore, the use of a carrier plate makes this method impossible to apply to an endoscopic system where the plate would need to travel though a convoluted or flexible corridor of varying shape.